| Summary: | 碩士 === 國立交通大學 === 電子工程系所 === 94 === In this thesis, several methods for channel estimation and data detection of OFDM systems in time-varying and multipath fading channels are investigated. Channel variations over an OFDM symbol destroy the orthogonality between subcarriers. The corresponding intercarrier-interference (ICI) degrades the system performance. This error floor becomes more severe as mobile speed, carrier frequency, or symbol duration increases. Based on the existing channel estimation methods and the data detection methods, several modifications to improve the system performances or to reduce the system computational complexities are proposed. The proposed data detection methods exploit time diversity involved in the nature of the time-varying channels. Thus, the proposed methods outperform the conventional methods, like ICI cancellation method and least square (LS) detection. For implementation, the proposed methods are modified to have acceptable complexities. The proposed channel estimation methods are based on appropriate mathematical models. The estimated parameters can be reduced by using these mathematical models. Therefore, channel estimation in fast fading channels becomes feasible and trackable.
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